Pneumatic hammer and counterbalanced suspension therefor



'A ug.15, 1967 A D iEZ ETAL I 3,335,805

. PNEUMATIC HAMMER AND COUNTERBALANCED SUSPENSION THEREFOR Filed Feb. 24, 1965 3 Sheets-Sheet 1 Inventors ADOLF DIEZ BY JOSEPH HEIM ATTORNEYS.

SION THEREFOR Aug; 15, 1967 A. DIEZ ETAL.

PNEUMATlC HAMMER AND COUNTERBALANCED SUSPEN 3 Sheets$heet 2:

Filed Feb. 24, 1965 Inventors ADOLF DIEZ A T TORNEYS.

Aug. 15, 11967 A. Quiz ETAL PNEUMATIC HAMMER AND COUNTERBALANCED SUSPENSION THEREFOR Filed Feb. 24, 19 5 Inventors ADOLF DIEZ JOSEPH HEIM A P m ATTORNEYS.

United States Patent 3,335,805 PNEUMATIC HAMMER AND COUNTERBAL- ANCED SUSPENSION THEREFOR Adolf Diez, Heilbronn, and Josef Helm, Oedheim, Germany, assignors to Karl Schmidt G.m.b.H., Neckarsulm (Wttgb), Germany, a corporation of Germany Filed Feb. 24, 1965, Ser. No. 434,958 Claims priority, application Germany, Mar. 6, 1964, Sch 34,760 4 Claims. (Cl. 173-121) This invention relates in general to pneumatic power tools, and more particularly to a pneumatically powered hammer and counterbalanced suspension therefor which is suitable for heavy duty use in foundries, as for example, for knocking-off risers and feedheads on castings.

Heretofore, it has been customary in foundry practice to remove risers, feedheads, and other metal projections from castings by manually powered conventional hammers, which for medium and relatively large castings, hammers weighing between 6 and 10 kilograms were used.

However, the size and strength of risers, etc. is dependent upon casting size, a factor which for extremely large castings can place the hammer momentum required for riser and feedhead removal beyond the physical capabilities of a human operator using a conventional hammer, or at least render the task of riser and feedhead removal extremely burdensome, and relatively inefiicient.

Thus, the pneumatic hammer of the instant invention, by reason of its high momentum hammerhead, is ideally suited for removing risers and feedheads from castings.

By suspending the pneumatic hammer from a jib crane or travelling hoist by means of a spiral spring counterbalance device according to the invention, said hammer can be easily moved and positioned almost eifortlessly as needed, thereby increasing the overall efficiency of riser and feedhead removal operations. The spiral spring counterbalance serves to take up the dead Weight of the pneumatic hammer which is preferably suspended at its center of gravity, and permits it to be selectively positioned at a desired height. To aid the operator in positioning the pneumatic hammer of the instant invention, a pair of longitudinally olfset handles, one of which can be hollow and serve as a pressurized air inlet, are provided.

Essentially the pneumatic hammer of the instant invention comprises a casing having a piston guide sleeve which is open at its forward end, a hammerhead piston slidably disposed within said guide sleeve, and controllable valve means for selectively pressurizing the guide sleeve to forcibly drive the hammerhead piston forward from an initial retracted position therein to deliver a hammer blow, and controllable means for restoring the hammerhead piston to its initial retracted position in the guide sleeve after a hammer blow has been delivered.

The guide sleeve, which is open at its forward end so as to permit the hammerhead portion of the piston to extend outward therefrom, as when delivering a hammer blow, is provided with a stop, such as an annular shoulder, to limit the forward travel of the piston so that it performs as a pneumatic hammer, rather than as a projectile shot from an air gun.

To provide the sudden pneumatic pressure force required to accelerate the hammerhead piston to a high kinetic energy level, a primary valve comparable in size to the guide sleeve is used for selectively admitting pressurized air into the guide sleeve to drive the piston.

The primary valve is arranged in the pneumatic hammer according to the invention so as to be normally closed, and is opened for delivering a hammer blow. Since by using a primary valve having a size of the same order of magnitude as the guide sleeve and piston, a relatively large valve opening force is required. This valve opening force 3,335,805 Patented Aug. 15, 1967 is supplied by an auxiliary pneumatic actuator operatively connected to the primary valve.

In turn, a control valve, which is manually operated, and is in flow connection with a source of pressurized air and the auxiliary pneumatic actuator, is provided for selectively pressurizing and venting said. actuator. When the control valve is in the configuration for pressurizing the auxiliary actuator, the primary valve is opened, whereas when said control valve is in the venting configuration, the primary valve is restored to its closed position.

Accordingly, to deliver a hammer blow, the control valve is placed in the pressurizing configuration, and to retract the hammerhead piston, said control valve is placed in its venting configuration. A restoring spring is preferably provided in the control valve for maintaining said valve in a normally venting configuration, thereby also maintaining the primary valve in a normally closed position.

It has been found that by using a primary pressurized air chamber integrally constructed with the pneumatic hammer casing, and which adjoins the guide sleeve, said air chamber being selectively placed in flow communication with said sleeve by the primary valve, a faster hammer blow can be delivered for a given. operating pneumatic pressure level than would be realized it the guide sleeve were supplied with pressurized air through a conventional pneumatic line. The air chamber is preferably constructed so as to have as great a volume as practical in relation to the hammerhead piston stroke displacement.

The reason for this preference is based upon the fact that the pneumatic hammer of the invention must, for practical reasons, be supplied with pressurizedair from a conventional source, preferably a constant pressure source, via a conventional flexible pneumatic line, which of practical necessity, has a much smaller cross sectional area than the guide sleeve. If such a pneumatic line were used directly for supplying the pressurized air to the guide sleeve, it would take longer to supply said sleeve with a volume of air corresponding to the hammerhead piston displacement, than would be required by using the comparatively large primary air chamber and primary valve according to the invention.

, Since in general, the pneumatic hammer of the instant invention will be used intermittently rather than continuously as in a vibrator type hammer, there will be suflicient time between hammer strokes to refill the primary air chamber. However, the pneumatic hammer of the instant invention can also be used continuously, i.e., to provide consecutive hammer blows as fast as the hammerhead piston can be retracted for repeat bolws, but with somewhat lower average hammer blow rate.

The basic pneumatic hammer of the instant invention can be modified by the inclusion of an intermediate hammerhead which is slidably mounted within the forward portion of the guide sleeve so as to have a limited axial travel therein when struck by the hammerhead piston. In this embodiment of the invention, the hammerhead piston never actually comes in contact with the workpiece, but delivers hammer blows thereto via the intermediate hammerhead.

By using an intermediate hammerhead as aforesaid, the guide sleeve is protected against the entry of chips, metal fragments, and other foreign matter which could result in jamming of the hammerhead piston.

If desired, the forward end of the guide sleeve can be provided with an outwardly beveled opening for preventing the penetration of foreign matter which could cause jamming.

It is therefore, an object of the invention to provide a pneumatic hammer which is capable of controllably delivering hammer blows of s ufiicient impact to remove risers, feedheads, and other metal projections from large castings.

Another object of the invention is to provide a pneumatic hammer as aforesaid which can be conveniently operated from a conventional pressurized air source.

Another and further object of the invention is to provide a pneumatic hammer as aforesaid which is relatively free from jamming by chips, metal fragments, and other foreign matter.

Still another and further object of the invention is to provide a counterbalanced suspension device for the aforesaid pneumatic hammer which will enable it to be moved and positioned with little effort.

Other and further objects and advantages of the invention will become apparent from the following detailed description and accompanying drawings in which:

FIG. 1 is a longitudinal view, partly in section, of a pneumatic hammer according to a preferred embodiment of the invention.

FIG. 2 is a side elevation view of the pneumatic hammer of FIG. 1 suspended by means of a spiral spring counterbalance device according to the invention.

FIG. 3 is a longitudinal view, partly in section, of a portion of a pneumatic hammer constructed in accordance with another embodiment of the invention.

FIG. 4 is a longitudinal view, partly in section, of a portion of a pneumatic hammer constructed in accordance with another and further embodiment of the invention.

FIG. 5 is a side view, partly in section, showing the details of the spiral spring counterbalance device illustrated in FIG. 2.

Referring now to FIG. 1, the pneumatic hammer H is preferably constructed with an assembled casing having a main body 11 and a cap member 12 fastened thereto. The main body 11 is generally hollow, and is provided with a pair of adjoining stepped cylindrical bores 13 and 14 which define a primary pressurized air chamber a and a hammerhead piston guide sleeve g, respectively.

A hammerhead piston f is slidably disposed within the sleeve g with a clearance of about 0.5 mm. and is provided with a forwardly disposed hammerhead portion 15 which is somewhat smaller in diameter than the forward end opening 16 of said sleeve g, so that said hammerhead portion 15 can be extended through and beyond said forward end opening 16 as when delivering a hammer blow.

To prevent the piston from being propelled out through the end of the sleeve g, a shoulder stop 17 is provided at the forward end of said sleeve g. A ring 18 of resilient material is preferably provided ahead of the stop 17 to cushion the impact of the piston 15 at the end of each hammer stroke.

The interior of the cap member 12 is generally hollow, and is provided with a cylindrical bore 19 in which an auxiliary piston c is slidably disposed. The cap member 12 and piston 0 function as an auxiliary pneumatic actuator 20 which is operatively connected via a hollow rod d to a primary valve e.

A closure member 21, which is inserted partially into the bore 13, serves as a hermetic separation seal between the primary air chamber a and that portion of the auxiliary actuator 20 bounded by the bore 19, pressure side 22 of piston 20, and end surface 23 of said closure member 21.

To facilitate manipulation of the pneumatic hammer H, a pair of longitudinally offset handles 24 and 25 are provided, which can be integrally formed with the main body 11, if desired, or made separately. By Way of example, the handle 25 is shown as being integrally constructed with the main body 11, and is provided with a central passage 26 which opens into the primary air chamber a, and a female threaded portion 27 for connection to a source of compressed air (not shown) by a conventional line or hose (not shown).

A control valve b, which is flow connected to the source of compressed air (not shown) via a passage 28-, and is also flow connected with the auxiliary actuator 20 via the passage 29 which is open at the surface 23, is provided for selectively pressurizing and venting the actuator 20. The valve b, which is constructed so as to be manually operable, is preferably provided with a spring 30 for maintaining it in a normally venting configuration. With valve b in the venting configuration, a spring i maintains the piston c in the position shown in FIG. 1.

The hollow rod d which passes through the closure member 21 with a slidable sealing fit, is connected to piston c, and to the primary valve e, and is of such a length that when the actuator 20 is vented, the primary valve e is pressed into sealing engagement with the shoulder 31 provided in the body 11 at the forward end of the air chamber a.

The piston c, and valve e are provided with passages 32 and 33 respectively, which together with the hollow portion of the rod 0., form a continuous open passage 34 extending from the working portion 35 of the sleeve g to the exhaust portion 36 of the bore 19, so as to enable said working portion 35 which is pressurized for driving the hammerhead piston f, to be vented through the hollow rod d after a hammer blow has been delivered.

A spring k connected at one end to the piston f, and at the other end to the cap member 12, is provided for restoring the piston f to the initial retracted position shown in FIG. 1 after a hammer blow has been delivered.

The operation of the pneumatic hammer H is best explained by considering its working parts to be in an initial configuration as shown in FIG. 1 with the handle 25 being connected to a source of compressed air (not shown) and the control valve b being in the vent position. Under these conditions, pressurized air will fill the chamber a and be confined therein by the closure member 21 and primary valve e. When the control valve b is placed in the pressurize position, compressed air from the aforesaid source will flow through passages 28, 29, and said valve b, and act upon the auxiliary piston c, urging it rearward overcoming the influence of the spring i and in sealing engagement against a resilient disc seal member 37, which seals the vent passage 34 to prevent the escape of pressurized air needed for driving the hammerhead piston 1. During this rearward movement of the auxiliary piston c, any air in the region 36 is expelled via the ports 1 extending through the cap member 12, along with any pressurized air which might initially flow through passage 34 before piston c can be sealed by the disc 37, since the opening of the primary valve e occurs simultaneously with the rearward movement of the auxiliary piston c.

It should be noted that in actual practice, the dimensions of the piston 0, rod d and sealing disc 37, are preferably selected so as to minimize this initial loss of pressurized air when the piston c begins to open valve e.

When passage 34 is sealed by the disc 37, the working region 35 of the sleeve g is pressurized, and the hammerhead piston f is forcibly driven forward to deliver a hammer blow.

To aid in the expulsion of air from the portion of said sleeve g ahead of the piston f, vent holes are provided; ust in case the opening 16 should be pressed against an obstructing surface (not shown).

As long as the control valve b is held in the pressurize position, the piston 1 will move forward until it is stopped by the cushion ring 18 and shoulder 17, and remain in such an extreme forward position until said valve b is restored to the vent position.

When the control valve b is restored to the vent positron, the auxiliary actuator 20 will be vented, and the plston 0 will be returned to the initial position shown in FIG. 1 by the spring i, thereby terminating the sealing engagement of said piston c with the disc 37, and permitting the pressurized air in the working region 35 to be discharged through the passage 34 and ports I. This discharge of pressurized air is aided by the spring k, which also operates to return the piston f to its initial retracted position as shown in FIG. 1.

The aforesaid sequence of events can be repeated as desired for consecutive hammer blows.

FIG. 4 illustrates an alternate sleeve g construction which may be incorporated into the embodiment of FIG. 1, if desired. An outwardly beveled portion s is provided at the forward end opening 16 of the sleeve g to prevent the entrance of metal chips and other foreign matter which might jam the piston f. The beveled portion s, cooperates with the oppositely beveled hammerhead portion 15 so that when the latter is driven forward, there is an annular wedge clearance zone for ejection of any chips or foreign matter which might be present at the end 16. This beveled portion s, has been found to be superior to the cylindrical counterpart of FIG. 1 in this regard. To provide for expulsion of air ahead of the piston, a plurality of small vent holes r, which can be covered with a screen, if desired, have been substituted for the larger holes h in FIG. 1, to further aid in eliminating the hazard of piston jamming by foreign matter. As will be apparent to those skilled in the art, the number of holes r can be selected to provide a suitable total venting area, and their size can be selected so as to exclude a chip or foreign particle above a given size.

FIG. 3 illustrates an alternate embodiment of the pneumatic hammer H of FIG. 1, wherein an intermediate hammer 0, which is slidably disposed within the sleeve 3 to be driven by the impact of the hammerhead piston j", is used for delivering hammer blows. The remainder of the pneumatic hammer H can be the same as that shown in FIG. 1.

The intermediate hammer o is mounted between a snap ring p and the cushion ring 18 or shoulder 17 of the cushion ring 18 is omitted, and is generally free to slidably travel therebetween. Dirt or broken pieces of metal, chips, etc., are prevented from entering through the open end 16 of the sleeve g by reason of the close fit between the outside diameter of the intermediate hammer and the diameter of the opening 16.

As in the case of the sleeve g construction described in connection with FIG. 4, a plurality of small vent holes r are provided, for proper venting ahead of both the piston and the intermediate hammer 0.

The embodiment of FIG. 3 offers an additional advantage in that when the hammerhead piston f strikes the intermediate hammer 0 and the latter moves forward, the air trapped between the shoulder 38 of said hammer 0 and the wall 14 of the sleeve g, i.e., in the annular region q, is compressed, thereby providing damping of the movement of said intermediate hammer 0. After a hammer blow has been struck, this compressed air in the region q will cause the hammer 0 to rebound slightly.

FIG. 2 illustrates generally, a manner in which a spiral spring counterbalance device in can be used to aid in the positioning of the pneumatic hammer H. In FIG. 2, a jib crane It provides support for the counterbalance device m, the hammer H, and its associated air pressure line 39 as well.

An eyebolt 40 fastened to the hammer H, preferably to its main body 11, and located thereon so that said hammer H is supported by a cable 41 force which passes through its center of gravity, is connected to the cable 41 which extends from the reel (not shown in FIG. 2) of the counterbalance device m. The housing (see detail in FIG. of the counterbalance m is in turn suspended by a cable 42 which is attached to a travelling hook 43 on the jib crane n.

FIG. 5 shows in detail a typical spiral spring counterbalance device m according to the invention, which can be used for suspending the pneumatic hammer H as illustrated in FIG. 2.

The counterbalance device m comprises a housing 44, an axle 45 mounted to said housing 44, a cable reel 46 rotatably mounted to the axle 45, and a spiral spring 6 47 attached at its inner end 48 to the axle 45, and at its outer end 49 to the reel 46.

An eye 50, which can be either integral with, or fastened to the housing 44, is provided for suspending the counterbalance device In by the cable 42, as in FIG. 2.

A pair of guides 51 are provided on the housing 44 for guiding the passage of the cable 41 as it is reeled in or paid out from the reel 46.

The spiral spring 47 provides a restoring force which tends to reel in the cable 41 onto the reel 46 until a length of cable 41 is wound thereupon which results in said spring 47 being in its equilibrium configuration. As the cable 41 is paid out, the spring 47 resists the unwinding action of the reel 46, so that when said cable 41 is connected to support the hammer H as in FIG. 2, the device In provides a counterbalance type of suspension to take up the dead weight of the hammer H, thereby facilitating its manipulation.

As can be readily noted, the combination of the counterbalance suspension device m and pneumatic hammer H as indicated by FIG. 2, results in a highly efi'icient work station.

In general, the various parts of the pneumatic hammer H, with the exception of sealing parts such as the disc 37, or cushioning parts as the ring 18, which are preferably made of a resilient material such. as rubber or a plastic can be made of a metal, such as aluminum or steel.

If desired, the hammerhead piston f, and also the intermediate hammer 0 can be weighted with a heavy metal such as lead, which can be encased within the interior of the piston f and/ or hammer 0.

It should be noted that the energy available in the hammer blows delivered by such a pneumatic hammer H will depend upon the weight of the piston f, and its striking velocity. By a suitable choice of operating pneumatic pressure, stroke length and piston 7 dimensions and weight, a pneumatic hammer H according to the invention can be designed to provide hammer blows of a selected energy level, with the application of merely routine engineering calculations. Thus, by using a sufiiciently high operating pressure, a relatively light hammerhead piston f can be used to deliver hammer blows of selected intensity.

What is claimed is:

1. A pneumatic hammer which comprises a hollow casing defining a guide sleeve open at its forward end, a primary air. chamber disposed for communication with a source of pressurized air, and an auxiliary air chamber, a hammerhead piston slidably disposed within said guide sleeve for movement relative thereto from a retracted position to an extended position for delivering a hammer blow, a first resilient means connected to said casing and to said hammerhead piston to urge same toward its retracted position, a normally closed primary valve disposed for movement into an open state to admit pressurized air from said primary chamber in to said guide sleeve behind the hammerhead piston to accelerate same against the effect of said first resilient means toward said extended position, an auxiliary piston slidably disposed within said auxiliary air chamber, a hollow rod connectng said primary valve and auxiliary piston together for movement in unison, said auxiliary piston and primary valve each having an open passage communicating with the hollow portion of said rod for venting said guide sleeve therethrough, a second resilient means connected to said casing and disposed to urge said auxiliary piston, hollow rod and primary valve into respective positions, corresponding to the normally closed state of said primary valve, and a control valve disposed for communication with a source of pressurized air, for communiaction with said auxiliary chamber, and for communication with the ambient atmosphere, said control valve being operable to selectively admit pressurized air into said auxiliary chamber to displace said auxiliary piston into a position wherein said primary valve is shifted to its open state thereby pressurizing the guide sleeve and accelerating the hammerhead piston to deliver a hammer blow at its extended position, said control valve being also operable to selectively vent said auxiliary chamber to the ambient atmopshere to restore said primary valve to its normally closed state under the influence of said second resilient means, and to return said hammerhead piston to its retracted position under the influence of said first resilient means.

2. The pneumatic hammer according to claim 1 Wherein said primary air chamber adjoins the piston guide sleeve, and the primary valve is normally disposed in sealing engagement across the interface of said air chamber and guide sleeve.

3. The pneumatic hammer according to claim 1 includ ing an intermediate hammer slidably disposed within said guide sleeve ahead of the hammerhead piston and adapted to be struck thereby for delivering a hammer blow.

4. The pneumatic hammer according to claim 3 wherein the intermediate hammer is provided with a peripheral flange for guidance Within said sleeve and the travel of 8 said intermediate hammer is limited by an internal shoul der of reduced diameter on said sleeve and disposed ad jacent to the forward end of said sleeve, and a snap ring mounted within and to said sleeve at a predetermined distance to the rear of said shoulder.

References Cited UNITED STATES PATENTS 730,839 6/1903 Peterson 254153 1,065,339 6/1913 Brazelle 173-134 2,722,918 11/1955 Kimball 173-133 2,734,488 2/1956 Wampach 173121 2,854,953 10/1958 Osborne 173121 2,998,148 8/1961 Hirnel 254153 X 3,094,901 6/1963 Wandel et al. 173-121 X FOREIGN PATENTS 137,792 6/ 1950 Australia.

20 FRED C. MATTERN, JR., Primary Examiner.

HALL C. COE, Examiner. 

1. A PNEUMATIC HAMMER WHICH COMPRISES A HOLLOW CASING DEFINING A GUIDE SLEEVE OPEN AT ITS FORWARD END, A PRIMARY AIR CHAMBER DISPOSED FOR COMMUNICATION WITH A SOURCE OF PRESSURIZED AIR, AND AN AUXILIARY AIR CHAMBER, A HAMMERHEAD PISTON SLIDABLY DISPOSED WITHIN SAID GUIDE SLEEVE FOR MOVEMENT RELATIVE THERETO FROM A RETRACTED POSITION TO AN EXTENDED POSITION FOR DELIVERING A HAMMER BLOW, A FIRST RESILIENT MEANS CONNECTED TO SAID CASING AND TO SAID HAMMERHEAD PISTON TO URGE SAME TOWARD ITS RETRACTED POSITION, A NORMALLY CLOSED PRIMARY VALVE DISPOSED FOR MOVEMENT INTO AN OPEN STATE TO ADMIT PRESSURIZED AIR FROM SAID PRIMARY CHAMBER IN TO SAID GUIDE SLEEVE BEHIND THE HAMMERHEAD PISTON TO ACCELERATE SAME AGAINST THE EFFECT OF SAID FIRST RESILIENT MEANS TOWARD SAID EXTENDED POSITION, AN AUXILIARY PISTON SLIDABLY DISPOSED WITHIN SAID AUXILIARY AIR CHAMBER, A HOLLOW ROD CONNECTING SAID PRIMARY VALVE AND AUXILIARY PISTON TOGETHER FORM MOVEMENT IN UNISON, SAID AUXILIARY PISTON AND PRIMARY VALVE EACH HAVING AN OPEN PASSAGE COMMUNICATING WITH THE HOLLOW PORTION OF SAID ROD FOR VENTING SAID GUIDE SLEEVE THERETHROUGH, A SECOND RESILIENT MEANS CONNECTED TO SAID CASING AND DISPOSED TO URGE SAID AUXILIARY PISTON, HOLLOW ROD AND PRIMARY VALVE INTO RESPECTIVE POSITIONS, CORRESPONDING TO THE NORMALLY CLOSED STATE OF SAID PRIMARY VALVE, AND A CONTROL VALVE DISPOSED FOR COMMUNICATION WITH A SOURCE OF PRESSURIZED AIR, FOR COMMUNICATION WITH SAID AUXILIARY CHAMBER, AND FOR COMMUNICATION WITH THE AMBIENT ATMOSPHERE, SAID CONTROL VALVE BEING OPERABLE TO SELECTIVELY ADMIT PRESSURIZED AIR INTO SAID AUXILIARY CHAMBER TO DISPLACE SAID AUXILIARY PISTON INTO A POSITION WHEREIN SAID PRIMARY VALVE IS SHIFTED TO ITS OPEN STATE THEREBY PRESSURIZING THE GUIDE SLEEVE AND ACCELERATING THE HAMMERHEAD PISTON TO DELIVER A HAMMER BLOW AT ITS EXTENDED POSITION, SAID CONTROL VALVE BEING ALSO OPERABLE TO SELECTIVELY VENT SAID AUXILIARY CHAMBER TO THE AMBIENT ATMOSPHERE TO RESTORE SAID PRIMARY VALVE TO ITS NORMALLY CLOSED STATE UNDER THE INFLUENCE OF SAID SECOND RESILIENT MEANS, AND TO RETURN SAID HAMMERHEAD PISTON TO ITS RETRACTED POSITION UNDER THE INFLUENCE OF SAID FIRST RESILIENT MEANS. 